SQL302 Intermediate SQL Workshop 1

SQL302

Intermediate SQL Programming
Based on SQL Clearly Explained by Jan Harrington and
Microsoft SQL Server2008 T-SQL Fundamentals by Itzik Ben-gan

Module 1 – Relational Database Background, CASE,
Cast & Convert, Subqueries, Table Expressions
Bookstore SQL302 Module 1 1

Note on SQL302 Slides
• Many of these slides were originally designed to
support a single SQL course which was used for any
of MS Access, MySQL, Oracle and SQL Server.
• As such you may see here slides developed in any
one of the above products.
• We are in the process of migrating the vendor
specific slides out into their own slide sets.

Bookstore2 SQL302 Module 2 2

Warning!
• Below are some table name changes to be
aware of in doing queries. We have created
synonyms so either name should work.

New Name Old Name
Orders Order_filled
Order_Lines Orderlines


SQL302 Contact Information

P.O. Box 6142
Laguna Niguel, CA 92607
949-489-1472
http://www.d2associates.com
slides.1@dhdursoassociates.com
Copyright 2001-2012. All rights reserved.


SQL302 Resources
• Bookstore database scripts found on
box.com at
http://tinyurl.com/SQLScripts
• Slides can be viewed on SlideShare…
http://www.slideshare.net/OCDatabases
• Follow up questions?
sql.support@dhdursoassociates.com


SQL Programming
• Course focus is SQL language
• Widely used for:
– Database administration
– Enterprise application development
– Data driven web sites
• A foundation skill for eBusiness and
almost all major business applications that
use relational databases

SQL302
• Students should have taken SQL202 or
have equivalent experience. It is assumed
students know basic SQL.
• We will use the Management Studio in this
class, but the focus will be on SQL
scripting


Relational Database Evolution
• Based on Codd’s paper
• Early commercial efforts focused on Unix
• First mainframe implementation by IBM -
precursor to today’s DB2
• First PC implementation in early 80’s by
Oracle


Relational Database Basics
• Storage • Indexes
• Databases • Views
• Tables • Cursors
• Rows • Application interfaces
• Columns


Relational Database Table


Constraints
• Database • Other Business Rule
– Domain – Triggers
– Uniqueness – Stored Procedures
– Relationship
Cardinality
• 1 to 1
• 1 to N


Relational Database with constraints


Database Management Systems

Positioning Chart

Cost VLDB
Enterprise
Workgroup
Single user
Spreadsheet
# Users

System Architecture

File Server
Architecture
Access
MDB

Access


System Architecture

Client/Server
Architecture
Oracle
SQL DB

Visual Access
Basic App


System Architecture

Web
Architecture
Web Oracle
Server DB

SQL
Browser


Approaching SQL
• Relatively simple
• Two main environments
– Interactive (This course)
– Embedded
• Static (Compiled)
• Dynamic


SQL Standardization
ANSI standardization
– First standard in 1986
– SQL 89
– SQL 92
– SQL 99
• Various vendor extensions
– Microsoft/Sybase: T-SQL
– Oracle: PL/SQL


SQL Conformance
• Entry
• Intermediate
• Advanced
• Most are at least entry level


SQL Statements

• Data Manipulation Language (DML)
• Data Control Language (DCL)
• Data Definition Language (DDL)

• Note: SQL 99 changes these to seven types
including DQL Data Query Language


SQL DDL
• Data definition language (DDL)

– Create, alter, drop, etc.
– Frequently implemented via various CASE
tools: Visio, Embarcadero, ERWin, etc.
– But very useful for database administration


SQL DCL
• Data Control Language (DDL)

– Grant
– Revoke
– Deny
– Constraints


SQL DQL
– Select


SQL DML
– Insert
– Update
– Delete


SQL Statement Processing

Parse

Validate

Optimize

Access Plan

Execute


Sample Database(s)

• Before we continue (note: instructor may have
already done this)…
• Load the sample database(s) if not already loaded
– Use supplied SQL Script (after class this script may be
found on Box.com).


Text Conventions
• In Access character strings are normally
surrounded by double quotes
– “Jones”
• In an enterprise database such as Oracle or
SQL Sever enclose text strings in single
quotes
– ‘Jones’


Date Conventions
• In an enterprise database such as Oracle or
SQL Sever, enclose dates in single quotes
– ‘2004-12-23’ MySQL
– ’12-23-2004’ SQL Server
– ’23-DEC-04’ Oracle


Select statement clauses
SELECT…
INTO…
FROM…
WHERE…
GROUP BY…
HAVING…
ORDER BY…

SELECT

See SQL202 for syntax and
semantics of basic SELECT
statement


On Your Own
• Find books written by Mark Twain
• Show title, publisher, year


Complex Predicates
Follow normal boolean logic
Select customer_last_name,
customer_street
From customers
Where (customer_last_name =
‘Jones’ or customer_last_name =
‘Smith’)and customer_state=‘NY’


Select with Complex Where


Complex Where Result


Special Operators
• Can be used in where clause
• Covered in this class (SQL302)
– Exists (Covered in section on Joins)
– Like extensions
– Any, some, all

• Previously Covered in SQL202
– LIKE
– IN
– BETWEEN
– IS NULL

Like Extensions
• ANSI wildcards
• Where
customer_last_name
like ‘[JK]o%’
like ‘[J-M]%’
like [^abc]%


Any, some, All
• Any, some • All
• Modifies comparison • Modifies comparison
operator operator
• Ex: expr > any (1,2,3) • Ex: expr > all(1,2,3)
means expr would would have to be
have to be greater greater than 3
than the minimum
which is 1


On Your Own
• Find all customers with a last name that starts
with a through m
• Find all customers that live in a state that does
not start with m


Case
• Used to return a choice from two or more
alternatives
• Two forms
– Searched case
– Unsearched case


Unsearched (Simple) CASE
• This form of case has a selector which
takes on a value used to select an
alternative
• Syntax:
Select case <selector>
When <value1> then <expr1>,
When <value2> then <expr2>,
…
Else
<statement>
End

Unsearched (Simple Case)
• Example: expand the order filled status
columns in the orders table


Searched CASE
• This form of the Case statement does not
have a selector
• Syntax:
Select case
When <condition1> then <expr1>,
When <condition2> then <expr2>,
…
Else
<statement>
End

Searched CASE
• Example: list names of referring
customers, self in no referrer


CAST
• Function to cast a column to a different
data type; same idea as cast in c
programming
• Syntax:
CAST ( expression AS data_type [ ( length ) ] )


CAST
• Example: combine author name and
publication year into one column


CAST results


Convert
• Function to convert from one data type to
another; mostly replaced by cast
• Syntax
CONVERT ( data_type [ ( length ) ] , expression
[ , style ] )


Convert
• Example:
– Remove time from display of a datetime
column


Convert results


Subqueries
• One select statement embedded in another
• Can be nested multiple levels deep
• Can be used in select, from and where
clauses
• Two types:
– Uncorrelated – executes inner query then outer
– Correlated – executes inner query once for
each outer query row


Uncorrelated Subquery
• In list (covered in sql202 basic class)
• Single valued


Uncorrelated Subquery

select isbn, quantity
from orderlines
where order_numb in
(select order_numb from
orders where order_date
between ‘1/1/99’ and
‘12/31/99’);

Single-valued Subquery
• Subqueries can be used where an
expression returns a scalar or single value
– calculations
– comparisons
• Can be used in select list, from clause and
where clause


Single-valued Subquery
• Example
– Show all orderlines with an order total greater
than the average for all orderlines
• Code
use bookstore;
SELECT isbn, quantity
, (select avg(quantity) from orderlines) as
[Average Quantity]
FROM orderlines AS ol
WHERE quantity >
(select avg(quantity) from orderlines)

Correlated Subquery with Exists
• Inner subquery executed once for each outer row
• Exists will return true or false depending on
whether the result will have any rows or not
• Can be a quick way to test for existence of
records (parent records, say) as used in
application enforcement of referential integrity


Correlated subquery with Exists
SELECT isbn, quantity
FROM orderlines AS ol
WHERE exists
(select * from orders o where
ol.order_numb = o.order_numb
and o.order_date between ‘1/1/99’
and ‘12/31/99’);


Derived Tables
• Sort of a named subquery
• Allows you to access columns inside the
subquery from the containing outer query
• Syntax
<select statement> as derivedtablename


Derived Tables
• Example: List the number of orders per
year
• Code
use bookstore;
select order_year, count(order_numb)
from(
select YEAR(order_date) as order_year,
order_numb
from orders) as d
group by order_year;

Common Table Expressions
• Can be used to define a subquery that can
be reused within an SQL statement
• Syntax
With CTE_name (column list)
As (
Select statement
)
<outer query that uses the CTE>


Common Table Expressions
• Example: show order_lines with cost more
than the average. Demonstrate two
techniques:
– Technique 1 - Using subqueries w/out a CTE
– Technique 2 - With CTE’s


Technique 1 – w/out CTE
select isbn, cost_each, (select
AVG(cost_each)from orderlines)
from orderlines
where cost_each > (select AVG(cost_each) from
orderlines)
order by isbn;


Technique 2 – using a CTE
with average_cost_cte(average_cost)
as
(select AVG(cost_each)
from orderlines)
select isbn, cost_each, average_cost
from orderlines, average_cost_cte
where cost_each > average_cost
order by isbn;


SQL Exercises
• List all customers whose last name does not
end with s or t.
• Find all customers who have not placed an
order.
• Find all order lines with an amount less than
the average. Include the order date without the
time.
• List all books with a price greater than the
average price for all books. Show the variance
from the average, too. Use a CTE.
Bookstore SQL302 Module 1 [end module] 63

Notes


SQL302 Intermediate SQL Workshop 1

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